359 Biochemical characterization of A- and B-type starch granules in wheat endosperm.

M. PENG (1,2), M. Gao (1), M. Båga (1), P. Hucl (2), and R. N. Chibbar (1). (1) National Research Council Canada, Plant Biotechnology Institute, 110 Gymnasium Place, Saskatoon, SK S7N 0W9, Canada; (2) University of Saskatchewan, Crop Development Centre, 51 Campus Drive, Saskatoon, SK, S7N 5A8, Canada.

Mature wheat (Triticum aestivum L.) endosperm contains two types of starch granules, the large A- and the small B-type. The two types of starch granules differ in their physical and chemical properties and also have different end uses. It is desirable to have wheat with uni-modal granule distribution. To genetically alter the granule size distribution in wheat it is imperative to identify genes that determine granule size. Therefore the objective of this study is to identify proteins specific to the two types of starch granules. We recently reported that centrifugal sedimentation through two Percoll solutions (70% v/v and 100% v/v) produced homogenous populations of A- and B-type starch granules (Peng et al., 1999, Cereal Chem. in press). The extracted surface and integral proteins from the purified A- and B-type starch granules were analyzed by denaturing polyacrylamide gel electrophoresis (SDS-PAGE). Western blot analysis using antibodies against starch branching enzymes and starch synthases, did not show any difference in these two group of enzymes between the A- and B-type starch granules. However, three polypeptides were specifically associated with the A-type starch granules. Results on the characterization of these polypeptides will be presented.